Python 获取子进程的pid
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obtaining pid of child process
提问by tazim
I am using python's multiprocessing module to spawn new process
我正在使用 python 的多处理模块来生成新进程
as follows :
如下 ：
import multiprocessing
import os
d = multiprocessing.Process(target=os.system,args=('iostat 2 > a.txt',))
d.start()
I want to obtain pid of iostat command or the command executed using multiprocessing module
我想获取 iostat 命令的 pid 或使用多处理模块执行的命令
When I execute :
当我执行：
d.pid
it gives me pid of subshell in which this command is running .
它给了我运行这个命令的子shell的pid。
Any help will be valuable .
任何帮助都是有价值的。
Thanks in advance
提前致谢
回答by whaley
I think with the multiprocess module you might be out of luck since you are really forking python directly and are given that Process object instead of the process you are interested in at the bottom of the process tree.
我认为使用 multiprocess 模块你可能不走运，因为你真的直接 fork python 并且在进程树的底部给出了 Process 对象而不是你感兴趣的进程。
An alternative way, but perhaps not optimal way, to get that pid is to use the psutilmodule to look it up using the pid obtained from your Process object. Psutil, however, is system dependent and will need to be installed separately on each of your target platforms.
获取该 pid 的另一种方法（但可能不是最佳方法）是使用psutil模块使用从 Process 对象获得的 pid 来查找它。但是，Psutil 依赖于系统，需要在每个目标平台上单独安装。
Note: I'm not currently at a machine I typically work from, so I can't provide working code nor play around to find a better option, but will edit this answer when I can to show how you might be able to do this.
注意：我目前不在我通常使用的机器上，因此我无法提供工作代码，也无法四处寻找更好的选择，但是我会在可以时编辑此答案以展示您如何能够做到这一点.
回答by Ilia Barahovski
For your example you may use the subprocesspackage. By default it executes the command without shell (like os.system()) and provides a PID:
对于您的示例，您可以使用该subprocess包。默认情况下，它在没有 shell 的情况下执行命令（如os.system()）并提供一个 PID：
from subprocess import Popen
p = Popen('iostat 2 > a.txt', shell=True)
processId = p.pid
p.communicate() # to wait until the end
The Popenalso provides ability to connect to standard input and output of the process.
的Popen还提供了连接到标准输入和过程输出的能力。
note: before using shell=Truebe aware of the security considerations.
注意：使用前shell=True要了解的安全注意事项。
回答by rakslice
Since you appear to be using Unix, you can use a quick pscommand to get the details of the child processes, like I did here (this is Linux-specific):
由于您似乎在使用 Unix，您可以使用快速ps命令来获取子进程的详细信息，就像我在这里所做的一样（这是 Linux 特定的）：
import subprocess, os, signal
def kill_child_processes(parent_pid, sig=signal.SIGTERM):
ps_command = subprocess.Popen("ps -o pid --ppid %d --noheaders" % parent_pid, shell=True, stdout=subprocess.PIPE)
ps_output = ps_command.stdout.read()
retcode = ps_command.wait()
assert retcode == 0, "ps command returned %d" % retcode
for pid_str in ps_output.split("\n")[:-1]:
os.kill(int(pid_str), sig)
回答by zhanxw
Similar to @rakslice, you can use psutil:
与@rakslice 类似，您可以使用psutil：
import signal, psutil
def kill_child_processes(parent_pid, sig=signal.SIGTERM):
try:
parent = psutil.Process(parent_pid)
except psutil.NoSuchProcess:
return
children = parent.children(recursive=True)
for process in children:
process.send_signal(sig)
回答by Ankur Agarwal
[me@localhost ~]$ echo $$
30399
[me@localhost ~]$ cat iostat.py
#!/usr/bin/env python3.4
import multiprocessing
import os
d = multiprocessing.Process(target=os.system,args=('iostat 2 > a.txt',))
d.start()
[me@localhost ~]$ ./iostat.py &
[1] 31068
[me@localhost ~]$ watch -n 3 'pstree -p 30399'
[me@localhost ~]$
This gave me the PID of iostatSee image. 
这给了我iostat查看图像的PID 。
